What’s New in Local Anesthetics?

Abstract

Summary Although no new local anesthetic agents were introduced into clinical practice during the past 10 years, a number of developments occurred in recent years with regard to agents for regional anesthesia. In terms of conventional local anesthetic drugs, ropivacaine represents a new amino-amide type of agent that has been extensively studied in laboratory animals. The results to date suggest that ropivacine may be capable of providing a prolonged duration of anesthesia, similar to bupivacaine, but with an improved margin of safety in terms of cardiovascular toxicity. In the field of topical analgesia, EM LA has already been studied extensively in clinical situations. This preparation, which consists of a eutectic mixture of lidocaine and prilocaine, may be the first useful means of providing effective topical cutaneous analgesia and should be of particular value in pediatric patients. Several novel types of local anesthetic preparations are currently being investigated. In this regard, the microdroplet formulation of methoxyflurane appears to provide prolonged periods of analgesia following local infiltration. The use of combinations of local anesthetics and opiates for prolonged analgesia also is an area of increasing interest. Low concentrations of local anesthetics with an opiate such as fentanyl are currently useful for continuous epidural analgesia during labor. In addition, such combinations are also valuable for prolonged postoperative pain relief. Carbonated solutions of local anesthetics, or the use of pH-ad-justed solutions by the addition of bicarbonate, appear useful to reduce the onset time of conduction blockade, particularly when employed for brachial plexus anesthesia.